/wɛər ˈlɛvəlɪŋ/
noun … “Evenly distribute writes to prolong memory lifespan.”
Wear Leveling is a technique used in non-volatile memory devices, such as Flash storage and SSDs, to prevent certain memory blocks from wearing out prematurely due to repeated program/erase cycles. Flash memory cells have a limited number of write cycles, and wear leveling distributes writes across the device to ensure all blocks age uniformly, extending the effective lifespan of the storage.
Key characteristics of Wear Leveling include:
- Static wear leveling: redistributes infrequently used blocks to balance usage across all memory cells.
- Dynamic wear leveling: monitors active write operations and directs them to less-used blocks.
- Longevity optimization: prevents early failure of hot spots by ensuring uniform usage.
- Transparency: usually handled by the memory controller, making it invisible to the host system or software.
- Integration: often combined with ECC and bad block management for reliability.
Workflow example: Writing data to an SSD:
function write_data(logical_address, data) {
physical_block = wear_leveling.select_block(logical_address)
flash.erase(physical_block)
flash.program(physical_block, data)
}Here, the wear leveling algorithm selects a physical block that has experienced fewer writes, erases it, and programs the new data, ensuring uniform wear across the device.
Conceptually, Wear Leveling is like rotating tires on a vehicle: by periodically moving high-use areas to different positions, the overall lifespan is extended, preventing some parts from wearing out too quickly.
See Flash, Memory, SSD, ECC, Non-Volatile Memory.